Matlab: Syntax error in arguments to LM-function???

I'm not very used to Matlab yet, and I suspect I'm doing a silly error with formating arguments for a Levenberg-Marquart function I want to use.

For the leasqr.m function [f,p,kvg,iter,corp,covp,covr,stdresid,Z,r2]= ...
leasqr(x,y,pin,F,stol,niter,wt,dp,dFdp,options)
I write:
leasqr([113,170,289,399,535,609,645],[210,143,89,79,12,162,206],{'ay','cy','ax','cx'},'y=f(cy-(ay*(ax*ax-(cx-x)^2)^(1/2))/ax)',0.1,10)

and get:
??? Function 'mtimes' is not defined for values of class 'cell'.

For the lma.m function[a,sd_a,var,covar,chisq] = lma(x,y,sig,a,funktion,parameter,accuracy,verbose) I write:
lma([113,170,289,399,535,609,645],[210,143,89,79,12,162,206],1,[100,300,200,400],'cy-(ay*(ax*ax-(cx-x)^2)^(1/2))/ax',{'ay','cy','ax','cx'})

and get:
??? Attempted to access g(2); index out of bounds because numel(g)=1.

I've tried different ,;[{('" signs to no avail. It seems it becomes "cells" or lacks elements.